Flashlamp Video

[Draco]

drat the tubes i have are only 10cm long so i will need to lower the power a bit more, not much though i think as they are 6mm id, i may see if a friend of mine can machine the electrodes, he i think as access to a real lathe
I am going to try and fire the xenon lamp that i have on hand,i have posted it before i also found another little lamp
DSC02692.JPG
the spacing is about 17mm and has 4mfd 2kv cap on the back with it's trigger coil, it came from England but the person i got it from did not know what it was used for

sorry if this is drifting from topic but i love flash lamps

[planters]

You need a specific energy input between 200 and 1500 J/cm3 to have the ablative regime !
You can use for the external wall plexiglass 10 to 20mm in tickness

Actually,the ablative regime begins when the silica and oxygen lines begin to appear and this occurs in low pressure discharges at about 35J/cm^3. With the appearance of the wall material there is also an increase in luminous efficiency. With small diameter lamps in the 1-2mm diameter range, the output begins to saturate at several hundred J/cm^3. With the larger lamps I have worked with in the 8-13.5mm range I have yet to reach any apparent saturation, but I'll work on it; I just received some REALLY big capacitors.

Plexiglas should work well although I haven't tried it. Despite the fact that it is a low melting point hydrocarbon, it is in fact the ablation products, whatever their origin, that are the source of the thermal radiation. The major downside of Plexiglas from my point of view is that it blocks UV. Depending on its particular composition and thickness this can begin as high as 300nm and is usually complete by 220nm. Unlike what I described as VUV absorption and re-emission by an ablating layer which should have nearly unity efficiency, UV absorption by the acrylic will likely be diffuse through its thickness and be manifest as heat. I down convert this UV into the dye absorbance band.

drat the tubes i have are only 10cm long so i will need to lower the power a bit more, not much though i think as they are 6mm id, i may see if a friend of mine can machine the electrodes, he i think as access to a real lathe

You are likely still OK. One paper I have shows that the 6mm lamp began to saturate at around 200J/cm^3. I wrote 150 as a conservative target.

sorry if this is drifting from topic but i love flash lamps

And arc lamps.

[planters]

I made a self contained digital meter with a 1000:1 divider all inside an old plexiglass box that uses an isolated battery for power,

Very nice wok by the way.

Femtoman,

You also do nice work.

That blue hazy appearance to the lamp after 100 pulses surprises me. The ablation process cleans the lamps and when run at low energies the un-ablated electrode sputter tends to be black. Might this be some dye or sealant material.

[femtoman]

Very nice wok by the way.

Femtoman,

You also do nice work.

That blue hazy appearance to the lamp after 100 pulses surprises me. The ablation process cleans the lamps and when run at low energies the un-ablated electrode sputter tends to be black. Might this be some dye or sealant material.

My flashlamp is a coaxial lamp and i work in the ablation regime at 500J/cm3 with very short pulse 500 to 600ns ( 2microFarads 25 kV)
In your video the flashlamp do not work in the ablating regime because the current intensity and the small surface not produce ablating regime (500 microfarads 3 kV) !
I have a discharge time 50 time shorter than you .
My flashlamp is optimised to pumping dye laser the annular section is 0.5mm thickness ( internal diameter 7mm and external diameter 8mm)
With long pulse more than 10 microsecond you have a glassing surface and with short pulse a thernisch surface!

Sorry my English is very bad!

[Draco]

To test my caps would you believe i went old school, very old school, Until i make the doubler for my main power supply i have been using a dynamotor I built a controller using the spare power supply from a PlayStation 3 and a pwm controller i had from another project, an unexpected advantage i came across is while the dynamotor is connected it discharges the cap bank when i ramp down the dynamotor, on 12 volts i get 425VDC. and on 24+ i can get 1kvdc but it stresses the thing.
the led read out is a cheap over seas made shunt to measure dc current draw, i still need to make a formal cabinet for it, the Dynamotor is just a classic cold war surplus, not that efferent but does the job
DSC02693.JPG


Femtoman, your English is just fine, no worries, it's even better then mine at times

[Draco]

my friend can indeed make the electrodes for me so all i need to do is makes the engineering drawings and supply him with the brass, it will take time but the work will be free, we barter , i fix his stuff and he can make parts for free, wish brings ip a question, i have been using the windows build in paint to make the drawings, is there anything free that works better then "paint" in a winblows platform?

[planters]

Draco,
As long as he is setting up, you probably should ask for something like 6 electrodes. You never know, once you have a pair of flashlamps you just might want to light up a little dye.

[planters]

Femtoman,


I am enjoying this discussion, but I have to disagree with you on several points. The wall ablation regime does indeed begin much lower than 200J/cm^3. This is supported in the literature where evidence of wall material begins to appear in the output spectrum and by analysis of the gas drawn out of the tube when operating in a flow through mode.

More than this, it can be demonstrated. Run a typical tube at low energies (below 20J/cm^3) for several hundred pulses. Observe the walls of the lamp near each electrode, especially if high erosion electrodes machined out of aluminum are used. There will be several cm of grey/black deposit that builds as the pulse count mounts. This material cannot be cleaned chemically, but a single higher energy pulse above approximately 50J/cm^3 will completely remove this material. If the tube is now run at this higher energy, the deposits do not return. This is why I questioned the tube in your image. It should be clean unless the material is not glass and the UV flux is causing some dye or other organic to be deposited.

Energies above 200J/cm^3 will be hard to achieve in real life tubes larger than 6mm ID. Indeed, in your coaxial tube with a 7mm OD inner tube and a 8mm ID outer tube which gives an annular gap of 0.5mm, multiplied by the tube length which I would estimate at 35cm gives a volume of approximately 4cm^3. Even at 500J you would only be at 125J/cm^3. By my measure you were well within the ablating regime, by yours, you were not much above 1/2 way to the bottom of the range.

Several decades ago when Russian researchers set the world record for a single dye laser pulse at 400J, they also used a coaxial lamp, however because of the large dimensions of their dye cell it may be that their lamp was not operating in the optimal loading range. They were using approximately 50kJ in an approximately 10us pulse. Based on some discussion by Duarte, it may be that the holy grail of short duration pumping may be less important than absolute peak power no matter the duration.

Although I suspect that pulse length has some significance it is not usually factored into the ablating threshold determination. It will most likely be that the shorter the pulse, the lower the transition from line emission to thermal radiation of wall products. I say this because a more rapid pulse will diffuse less into the bulk of the glass, reserving the energy and increasing the surface temperature. Nevertheless, I am seeing ablation in my 16us pulses.

[Draco]

Draco,
As long as he is setting up, you probably should ask for something like 6 electrodes. You never know, once you have a pair of flashlamps you just might want to light up a little dye.

I talked to my friend last night and he tells me that he can makes them i just need to supply him with the materials and make up a drawing, i have been using "paint" in windows but was wondering if there is a free version of CAD around? using paint works but the time it takes sucks.

I am almost positive he wont mind making more then one set, thanks for that idea!

[turbohead]

I talked to my friend last night and he tells me that he can makes them i just need to supply him with the materials and make up a drawing, i have been using "paint" in windows but was wondering if there is a free version of CAD around? using paint works but the time it takes sucks.

I am almost positive he wont mind making more then one set, thanks for that idea!

You can just use the old fashioned method of drawing a the design on a piece of paper, take a picture of the drawing and then send it too him.